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From f62231a54abff6566415ea82aa8773e61f5688d6 Mon Sep 17 00:00:00 2001
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From: Michal Sekletar <msekleta@redhat.com>
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Date: Tue, 15 Mar 2022 19:02:05 +0100
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Subject: [PATCH] core: shorten long unit names that are based on paths and
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 append path hash at the end
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Fixes #18077
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(cherry picked from commit 1d0727e76fd5e9a07cc9991ec9a10ea1d78a99c7)
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Resolves: #1940973
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---
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 src/basic/string-util.h   | 23 +++++-----
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 src/basic/unit-name.c     | 88 ++++++++++++++++++++++++++++++++++++++-
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 src/basic/unit-name.h     |  3 ++
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 src/core/mount.c          |  3 ++
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 src/test/test-unit-name.c | 25 ++++++++++-
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 5 files changed, 129 insertions(+), 13 deletions(-)
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diff --git a/src/basic/string-util.h b/src/basic/string-util.h
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index 742b566932..0d406ff64a 100644
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--- a/src/basic/string-util.h
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+++ b/src/basic/string-util.h
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@@ -9,17 +9,18 @@
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 #include "macro.h"
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 /* What is interpreted as whitespace? */
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-#define WHITESPACE        " \t\n\r"
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-#define NEWLINE           "\n\r"
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-#define QUOTES            "\"\'"
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-#define COMMENTS          "#;"
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-#define GLOB_CHARS        "*?["
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-#define DIGITS            "0123456789"
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-#define LOWERCASE_LETTERS "abcdefghijklmnopqrstuvwxyz"
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-#define UPPERCASE_LETTERS "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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-#define LETTERS           LOWERCASE_LETTERS UPPERCASE_LETTERS
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-#define ALPHANUMERICAL    LETTERS DIGITS
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-#define HEXDIGITS         DIGITS "abcdefABCDEF"
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+#define WHITESPACE          " \t\n\r"
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+#define NEWLINE             "\n\r"
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+#define QUOTES              "\"\'"
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+#define COMMENTS            "#;"
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+#define GLOB_CHARS          "*?["
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+#define DIGITS              "0123456789"
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+#define LOWERCASE_LETTERS   "abcdefghijklmnopqrstuvwxyz"
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+#define UPPERCASE_LETTERS   "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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+#define LETTERS             LOWERCASE_LETTERS UPPERCASE_LETTERS
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+#define ALPHANUMERICAL      LETTERS DIGITS
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+#define HEXDIGITS           DIGITS "abcdefABCDEF"
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+#define LOWERCASE_HEXDIGITS DIGITS "abcdef"
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 #define streq(a,b) (strcmp((a),(b)) == 0)
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 #define strneq(a, b, n) (strncmp((a), (b), (n)) == 0)
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diff --git a/src/basic/unit-name.c b/src/basic/unit-name.c
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index f9b3fafd4d..65ed979e39 100644
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--- a/src/basic/unit-name.c
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+++ b/src/basic/unit-name.c
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@@ -6,11 +6,17 @@
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 #include <stdlib.h>
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 #include <string.h>
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+#include "sd-id128.h"
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+
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 #include "alloc-util.h"
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 #include "glob-util.h"
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 #include "hexdecoct.h"
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 #include "path-util.h"
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+#include "random-util.h"
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+#include "siphash24.h"
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+#include "sparse-endian.h"
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 #include "special.h"
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+#include "stdio-util.h"
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 #include "string-util.h"
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 #include "strv.h"
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 #include "unit-name.h"
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@@ -31,6 +37,9 @@
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         VALID_CHARS_WITH_AT                     \
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         "[]!-*?"
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+#define LONG_UNIT_NAME_HASH_KEY SD_ID128_MAKE(ec,f2,37,fb,58,32,4a,32,84,9f,06,9b,0d,21,eb,9a)
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+#define UNIT_NAME_HASH_LENGTH_CHARS 16
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+
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 bool unit_name_is_valid(const char *n, UnitNameFlags flags) {
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         const char *e, *i, *at;
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@@ -513,6 +522,68 @@ int unit_name_template(const char *f, char **ret) {
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         return 0;
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 }
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+bool unit_name_is_hashed(const char *name) {
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+        char *s;
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+
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+        if (!unit_name_is_valid(name, UNIT_NAME_PLAIN))
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+                return false;
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+
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+        assert_se(s = strrchr(name, '.'));
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+
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+        if (s - name < UNIT_NAME_HASH_LENGTH_CHARS + 1)
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+                return false;
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+
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+        s -= UNIT_NAME_HASH_LENGTH_CHARS;
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+        if (s[-1] != '_')
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+                return false;
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+
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+        for (size_t i = 0; i < UNIT_NAME_HASH_LENGTH_CHARS; i++)
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+                if (!strchr(LOWERCASE_HEXDIGITS, s[i]))
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+                        return false;
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+
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+        return true;
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+}
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+
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+int unit_name_hash_long(const char *name, char **ret) {
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+        _cleanup_free_ char *n = NULL, *hash = NULL;
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+        char *suffix;
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+        le64_t h;
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+        size_t len;
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+
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+        if (strlen(name) < UNIT_NAME_MAX)
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+                return -EMSGSIZE;
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+
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+        suffix = strrchr(name, '.');
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+        if (!suffix)
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+                return -EINVAL;
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+
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+        if (unit_type_from_string(suffix+1) < 0)
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+                return -EINVAL;
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+
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+        h = htole64(siphash24(name, strlen(name) + 1, LONG_UNIT_NAME_HASH_KEY.bytes));
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+
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+        hash = hexmem(&h, sizeof(h));
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+        if (!hash)
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+                return -ENOMEM;
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+
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+        assert_se(strlen(hash) == UNIT_NAME_HASH_LENGTH_CHARS);
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+
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+        len = UNIT_NAME_MAX - 1 - strlen(suffix+1) - UNIT_NAME_HASH_LENGTH_CHARS - 2;
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+        assert(len > 0 && len < UNIT_NAME_MAX);
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+
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+        n = strndup(name, len);
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+        if (!n)
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+                return -ENOMEM;
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+
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+        if (!strextend(&n, "_", hash, suffix, NULL))
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+                return -ENOMEM;
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+        assert_se(unit_name_is_valid(n, UNIT_NAME_PLAIN));
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+
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+        *ret = TAKE_PTR(n);
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+
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+        return 0;
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+}
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+
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 int unit_name_from_path(const char *path, const char *suffix, char **ret) {
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         _cleanup_free_ char *p = NULL, *s = NULL;
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         int r;
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@@ -532,7 +603,19 @@ int unit_name_from_path(const char *path, const char *suffix, char **ret) {
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         if (!s)
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                 return -ENOMEM;
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-        /* Refuse this if this got too long or for some other reason didn't result in a valid name */
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+        if (strlen(s) >= UNIT_NAME_MAX) {
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+                _cleanup_free_ char *n = NULL;
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+
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+                log_debug("Unit name \"%s\" too long, falling back to hashed unit name.", s);
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+
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+                r = unit_name_hash_long(s, &n);
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+                if (r < 0)
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+                        return r;
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+
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+                free_and_replace(s, n);
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+        }
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+
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+        /* Refuse if this for some other reason didn't result in a valid name */
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         if (!unit_name_is_valid(s, UNIT_NAME_PLAIN))
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                 return -EINVAL;
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@@ -582,6 +665,9 @@ int unit_name_to_path(const char *name, char **ret) {
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         if (r < 0)
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                 return r;
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+        if (unit_name_is_hashed(name))
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+                return -ENAMETOOLONG;
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+
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         return unit_name_path_unescape(prefix, ret);
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 }
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diff --git a/src/basic/unit-name.h b/src/basic/unit-name.h
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index 61abcd585b..602295af8f 100644
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--- a/src/basic/unit-name.h
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+++ b/src/basic/unit-name.h
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@@ -45,6 +45,9 @@ int unit_name_replace_instance(const char *f, const char *i, char **ret);
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 int unit_name_template(const char *f, char **ret);
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+int unit_name_hash_long(const char *name, char **ret);
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+bool unit_name_is_hashed(const char *name);
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+
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 int unit_name_from_path(const char *path, const char *suffix, char **ret);
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 int unit_name_from_path_instance(const char *prefix, const char *path, const char *suffix, char **ret);
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 int unit_name_to_path(const char *name, char **ret);
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diff --git a/src/core/mount.c b/src/core/mount.c
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index d37b5731f8..e69ecb7ce3 100644
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--- a/src/core/mount.c
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+++ b/src/core/mount.c
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@@ -572,6 +572,9 @@ static int mount_add_extras(Mount *m) {
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         if (!m->where) {
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                 r = unit_name_to_path(u->id, &m->where);
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+                if (r == -ENAMETOOLONG)
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+                        log_unit_error_errno(u, r, "Failed to derive mount point path from unit name, because unit name is hashed. "
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+                                                   "Set \"Where=\" in the unit file explicitly.");
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                 if (r < 0)
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                         return r;
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         }
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diff --git a/src/test/test-unit-name.c b/src/test/test-unit-name.c
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index 2b00ef8cb7..35cfaafd30 100644
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--- a/src/test/test-unit-name.c
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+++ b/src/test/test-unit-name.c
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@@ -82,6 +82,7 @@ static void test_unit_name_replace_instance(void) {
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 static void test_unit_name_from_path_one(const char *path, const char *suffix, const char *expected, int ret) {
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         _cleanup_free_ char *t = NULL;
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+        int r;
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         assert_se(unit_name_from_path(path, suffix, &t) == ret);
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         puts(strna(t));
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@@ -89,12 +90,31 @@ static void test_unit_name_from_path_one(const char *path, const char *suffix, c
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         if (t) {
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                 _cleanup_free_ char *k = NULL;
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-                assert_se(unit_name_to_path(t, &k) == 0);
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+
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+                /* We don't support converting hashed unit names back to paths */
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+                r = unit_name_to_path(t, &k);
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+                if (r == -ENAMETOOLONG)
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+                        return;
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+                assert(r == 0);
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+
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                 puts(strna(k));
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                 assert_se(path_equal(k, empty_to_root(path)));
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         }
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 }
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+static void test_unit_name_is_hashed(void) {
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+        assert_se(!unit_name_is_hashed(""));
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+        assert_se(!unit_name_is_hashed("foo@bar.service"));
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+        assert_se(!unit_name_is_hashed("foo@.service"));
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+        assert_se(unit_name_is_hashed("waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_7736d9ed33c2ec55.mount"));
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+        assert_se(!unit_name_is_hashed("waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_7736D9ED33C2EC55.mount"));
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+        assert_se(!unit_name_is_hashed("waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!7736d9ed33c2ec55.mount"));
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+        assert_se(!unit_name_is_hashed("waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_7736d9gd33c2ec55.mount"));
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+        assert_se(!unit_name_is_hashed("waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_.mount"));
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+        assert_se(!unit_name_is_hashed("waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_2103e1466b87f7f7@waldo.mount"));
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+        assert_se(!unit_name_is_hashed("waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_2103e1466b87f7f7@.mount"));
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+}
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+
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 static void test_unit_name_from_path(void) {
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         puts("-------------------------------------------------");
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         test_unit_name_from_path_one("/waldo", ".mount", "waldo.mount", 0);
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@@ -105,6 +125,8 @@ static void test_unit_name_from_path(void) {
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         test_unit_name_from_path_one("///", ".mount", "-.mount", 0);
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         test_unit_name_from_path_one("/foo/../bar", ".mount", NULL, -EINVAL);
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         test_unit_name_from_path_one("/foo/./bar", ".mount", NULL, -EINVAL);
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+        test_unit_name_from_path_one("/waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", ".mount",
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+                                     "waldoaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_7736d9ed33c2ec55.mount", 0);
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 }
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 static void test_unit_name_from_path_instance_one(const char *pattern, const char *path, const char *suffix, const char *expected, int ret) {
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@@ -824,6 +846,7 @@ int main(int argc, char* argv[]) {
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         test_unit_name_is_valid();
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         test_unit_name_replace_instance();
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+        test_unit_name_is_hashed();
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         test_unit_name_from_path();
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         test_unit_name_from_path_instance();
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         test_unit_name_mangle();